JP2007294007A - Disk drive device and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce errors caused by aged deterioration of a heater which adjusts clearance between a head and a disk. <P>SOLUTION: A TFC control part 231 executes measurement of a resistance value of the heater in preset timing. The TFC control part 231 determines whether or not the measured resistance value is within a predetermined reference range. When the measured resistance value is within the reference range, processing is terminated as it is. When the measured resistance value is out of the reference range, the TFC control part 231 executes error response processing to resistance failure. As one of the error response processing, the TFC control part 231 notifies a host 51 that an abnormality (poor resistance) is detected in a resistance value of a TFC heater (ALERT). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a disk drive device and a control method thereof, and more particularly to heater control of a disk drive device including a heater for adjusting a clearance between a head element unit and a disk.

  As a disk drive device, a device using a disk of various modes such as an optical disk, a magneto-optical disk or a flexible magnetic disk is known. Among them, a hard disk drive (HDD) is used as a computer storage device. It has become widespread and has become one of the storage devices that are indispensable in current computer systems. Furthermore, the use of HDDs such as a removable memory used in a moving image recording / reproducing apparatus, a car navigation system, a mobile phone, a digital camera, etc. is expanding more and more due to its excellent characteristics.

  The magnetic disk used in the HDD has a plurality of data tracks formed concentrically, and each data track has a plurality of data including a plurality of servo data having address information and user data. A sector is recorded. A plurality of data sectors are recorded between each servo data. The head element part of the head slider supported by the oscillating actuator accesses the desired data sector according to the servo data address information, thereby writing data to the data sector and reading data from the data sector. It can be performed.

In order to improve the recording density of the magnetic disk, it is important to reduce the clearance between the head element portion that floats on the magnetic disk and the magnetic disk. For this reason, several mechanisms for adjusting the clearance have been proposed. One of them is provided with a heater in the head slider, and the clearance is adjusted by heating the head element portion with the heater. In this specification, this is called TFC (Thermal Flyheight Control). The TFC supplies a current to the heater to generate heat, and causes the head element portion to protrude by thermal expansion. As a result, the clearance between the magnetic disk and the head element portion is reduced. About TFC, it is disclosed by patent document 1, for example. Patent Document 1 discloses that a resistance value of a heater element that varies depending on temperature is measured, and that the output to the heater element is adjusted so as to compensate the heater power in accordance with the measured value.
US20050213143

  The TFC repeats ON / OFF of the heater several trillion times during use of the HDD. For this reason, there is a concern about the long-term reliability of TFC. From the investigation by the inventors, it has been found that by repeating ON / OFF of the heater by TFC, the heater material causes metal fatigue due to thermal expansion and contraction, and the heater can be disconnected or short-circuited due to electromigration. In addition, cracks due to material differences may occur at the boundary between the heater and surrounding members. Therefore, it is required to accurately detect or predict the deterioration of the heater element and perform a process corresponding to it.

  A disk drive device according to an aspect of the present invention includes a slider that floats on a rotating disk, a head element portion that is disposed on the slider, and a head element portion that is disposed on the slider and protrudes by thermal expansion. A heater for adjusting a clearance between the disk, a measurement circuit for measuring a resistance value of the heater at a preset timing, and determining whether the heater has a resistance failure with reference to the measured resistance value; A controller is provided for performing error handling processing when the resistance is defective. By monitoring the resistance value of the heater and performing an error handling process when the resistance is defective, errors due to deterioration of the heater resistance over time can be reduced. In a preferred example, the controller notifies the host of a resistance failure of the heater in the error handling process. As a result, processing corresponding to the deterioration of the heater can be performed on the host side.

  The controller preferably performs a confirmation process of user data written by the head element unit in the error handling process. When the clearance is increased due to heater deterioration, data write errors can be reduced. Further, when the temperature detected by the temperature detector is equal to or lower than the reference temperature, the controller performs confirmation processing of user data written by the head element unit. As a result, it is possible to reduce data write errors while suppressing performance degradation. In addition, when the heater is driven at a constant current, the controller performs a process of confirming user data written by the head element unit when the resistance value of the heater falls outside a reference range. Alternatively, when the heater is driven at a constant voltage, the controller performs a process of confirming user data written by the head element unit when the resistance value of the heater increases outside the reference range.

  As a preferred example, the controller increases the frequency of measuring the resistance value of the heater in the error handling process. As a result, it is possible to more reliably detect subsequent deterioration of the heater. The controller reduces the slew rate of the output to the heater in the error handling process. Thereby, deterioration of the heater can be suppressed.

  Preferably, the controller determines the heater as a defective resistance when a change in the resistance value of the heater with respect to a preset value is 10% or more. As a result, errors due to heater open / short can be prevented more reliably.

  Preferably, the controller further determines a resistance failure of the heater with reference to a read amplitude of the head element unit. Thereby, more accurate resistance defect determination can be performed. Further, the controller performs the error handling process when the resistance value of the heater is outside the reference range and when the resistance value of the heater is within the reference range and the change in the read amplitude is outside the reference range. Do.

  Preferably, the controller further determines resistance failure of the heater with reference to an error rate of data read by the head element unit. Thereby, more accurate resistance defect determination can be performed. The controller performs the error handling process when the resistance value of the heater is out of a reference range and when the resistance value of the heater is within the reference range and the change in the error rate exceeds the reference.

  According to another aspect of the present invention, there is provided a slider that floats on a rotating disk, a head element portion disposed on the slider, and a head element portion disposed on the slider that protrudes due to thermal expansion. And a heater for adjusting the clearance of the disk drive device. In this method, the resistance value of the heater is measured at a preset timing, the resistance value is determined with reference to the measured resistance value, and if it is determined that the resistance is defective, the error is detected. Perform response processing. By monitoring the resistance value of the heater and performing an error handling process when the resistance is defective, errors due to deterioration of the heater resistance over time can be reduced.

  According to the present invention, it is possible to reduce an error due to aged deterioration of the heater resistance that adjusts the clearance between the head and the disk.

  Hereinafter, embodiments to which the present invention can be applied will be described. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Moreover, in each drawing, the same code | symbol is attached | subjected to the same element and the duplication description is abbreviate | omitted as needed for clarification of description. In the following, embodiments of the present invention will be described by taking a hard disk drive (HDD) as an example of a disk drive device as an example.

  One of the characteristic points of the present embodiment is the heater resistance failure determination and error handling processing for it in TFC (Thermal Fly height Control) of the disk drive device. The TFC adjusts the clearance between the head element portion and the recording disk by thermal expansion due to heat from the heater on the slider. The HDD according to this embodiment measures the heater resistance value, and executes an error handling process for the resistance failure. Thereby, deterioration of the heater is suppressed, or an error when TFC is not sufficiently performed is reduced.

  In order to facilitate understanding of the feature points of this embodiment, first, an outline of the entire configuration of the HDD will be described. FIG. 1 is a block diagram schematically showing the overall configuration of the HDD 1 according to the present embodiment. As shown in FIG. 1, an HDD 1 includes a sealed enclosure 10 and a magnetic disk 11, which is an example of a recording disk (recording medium), a head slider 12, an arm electronic circuit (AE: Arm Electronics) 13, a spindle disk. A motor (SPM) 14, a voice coil motor (VCM) 15, an actuator 16 and a temperature detector 19 are provided.

The HDD 1 further includes a circuit board 20 fixed to the outside of the enclosure 10. On the circuit board 20, each IC such as a read / write channel (RW channel) 21, a motor driver unit 22, a hard disk controller (HDC) and an MPU integrated circuit (hereinafter referred to as HDC / MPU) 23, and a RAM 24. It has. Each circuit configuration can be integrated into one IC, or can be divided into a plurality of ICs.
User data from the external host 51 is received by the HDC / MPU 23 and written to the magnetic disk 11 by the head slider 12 via the RW channel 21 and the AE 13. The user data stored in the magnetic disk 11 is read by the head slider 12, and the user data is output from the HDC / MPU 23 to the external host 51 via the AE 13 and the RW channel 21.

  The magnetic disk 11 is fixed to the SPM 14. The SPM 14 rotates the magnetic disk 11 at a predetermined angular velocity. The motor driver unit 22 drives the SPM 14 according to control data from the HDC / MPU 23. The magnetic disk 11 of this example has recording surfaces for recording data on both sides, and a head slider 12 corresponding to each recording surface is provided. Each head slider 12 includes a slider that floats on the magnetic disk, and a head element unit that is fixed to the slider and converts between a magnetic signal and an electric signal. The head slider 12 of this embodiment is provided with a heater for TFC that adjusts the clearance (flying height) between the head element portion and the magnetic disk 11 by heating. The structure of the head slider 12 will be described in detail later with reference to FIG.

  Each head slider 12 is fixed to the tip of the actuator 16. The actuator 16 is connected to the VCM 15, and moves in the radial direction on the magnetic disk 11 that rotates the head slider 12 by rotating about the rotation axis. The motor driver unit 22 drives the VCM 15 according to control data (referred to as DACOUT) from the HDC / MPU 23. One or more magnetic disks 11 may be provided, and the recording surface can be formed on one side or both sides of the magnetic disk 11.

  The AE 13 selects one head element unit 12 that accesses the magnetic disk 11 from the plurality of head element units 12, and amplifies a reproduction signal reproduced by the selected head element unit 12 with a constant gain. To the RW channel 21. Further, the recording signal from the RW channel 21 is sent to the selected head element unit 12. The AE 13 further functions as an adjustment circuit that supplies current (electric power) to the heater and adjusts the amount of the current.

  In the read process, the RW channel 21 amplifies the read signal supplied from the AE 13 so as to have a constant amplitude, extracts data from the acquired read signal, and performs a decoding process. Data to be read out includes user data and servo data. The decoded read user data and servo data are supplied to the HDC / MPU 23. In the write process, the RW channel 21 code-modulates the write data supplied from the HDC / MPU 23, further converts the code-modulated write data into a write signal, and supplies the write signal to the AE 13.

  In the HDC / MPU 23, the MPU operates according to the microcode loaded in the RAM 24. As the HDD 1 starts up, the RAM 24 is loaded with data necessary for control and data processing from the magnetic disk 11 or ROM (not shown), in addition to the microcode operating on the MPU. The HDC / MPU 23 includes data such as read / write processing control, command execution order management, head element unit 12 positioning control (servo control) using servo signals, interface control, defect management, and ERP when an error occurs. Necessary processing related to the processing and overall control of the HDD 1 are executed. In particular, the HDC / MPU 23 of this embodiment performs TFC heater resistance measurement and error handling processing when the measured value indicates defective resistance. This point will be described later.

  Next, the configuration of the TFC head slider 12 in this embodiment will be described. FIG. 2 is a cross-sectional view showing a partial configuration of the head slider 12 in the vicinity of the air outflow end surface (trailing side end surface) 121. The magnetic disk 11 rotates from left to right in FIG. The head slider 12 includes a head element unit 122 and a slider 123 that supports the head element unit 122. The TFC of this embodiment can be applied to both perpendicular magnetic recording and horizontal magnetic recording HDDs.

  The head element unit 122 reads and writes magnetic data from and to the magnetic disk 11. The head element unit 122 includes a read element 32 and a write element 31 on the trailing side. The write element 31 is an inductive element that generates a magnetic field between the magnetic poles 312 with a current flowing through the write coil 311 and records magnetic data on the magnetic disk 11. The read element 32 is a magnetoresistive element, and includes a magnetoresistive element 32 a having magnetic anisotropy, and the magnetic data recorded on the magnetic disk 11 by the resistance value that changes according to the magnetic field from the magnetic disk 11. read out.

  The head element portion 122 is formed on an AlTiC substrate constituting the slider 123 using a thin film forming process such as plating, sputtering, and polishing. The magnetoresistive element 32 a is sandwiched between magnetic shields 33 a and b, and the write coil 311 is surrounded by an insulating film 313. The head element portion 122 includes a protective film 34 such as alumina around the write element 31 and the read element 32, and the entire head element portion 122 is protected by the protective film 34. In the vicinity of the write element 31 and the read element 32, a heater 124 is formed by a thin film process using a thin film resistor. In this example, the heater 124 is located on the side of the head element portion 122 opposite to the diamagnetic disk 11. The heater 124 can be formed by meandering a thin film resistor using permalloy and filling the gap with alumina.

  When the AE 13 supplies a current to the heater 124 (when electric power is supplied), the vicinity of the head element portion 122 is projected and deformed by the heat of the heater 124. At the time of non-heating, the ABS surface of the head slider 12 has a shape indicated by S1, and a clearance that is a distance between the head element portion 122 and the magnetic disk is indicated by C1. The protruding shape S2 when the heater 124 is heated is schematically shown by a broken line in FIG. The head element unit 122 approaches the magnetic disk 11, and the clearance C2 at this time is smaller than the clearance C1. FIG. 2 is a conceptual diagram, and the dimensional relationship is not accurate. For example, the protruding surface shape S2 has a protruding amount of nanometer order (several nanometers).

  By repeatedly expanding and expanding the head element portion 122 by TFC, the material of the heater 124 may undergo metal fatigue due to thermal expansion and contraction, and the heater 124 may be disconnected or short-circuited due to electromigration. In addition, cracks due to material differences may occur at the boundary between the heater 124 and the surrounding members. If the heater 124 is opened / shorted, the HDD 1 cannot execute TFC, which causes trouble in reading / writing user data. Therefore, before the heater 124 is opened / shorted, the HDD 1 is required to detect a tendency of abnormality of the heater 124 and perform processing corresponding thereto.

  The HDD 1 of this embodiment measures the resistance value of the heater 124 at a preset timing. When the resistance value indicates a preset defective resistance value, the HDD 1 executes an error handling process corresponding thereto. Specifically, as shown in the block diagram of FIG. 3, the TFC control unit 231 controls the resistance value measurement of the heater 124 and the execution of the error handling process corresponding to the case where the resistance value indicates an error.

  The MPU that operates according to the micro code functions as the TFC control unit 231, or the TFC control unit 231 is implemented by a combination of some hardware circuits in the HDC / MPU 23 and the MPU that operates according to the micro code. Can do. The HDC / MPU 23 also functions as the RW processing unit 232. Typically, a combination of a part of hardware circuits in the HDC / MPU 23 and an MPU that operates according to microcode functions as the RW processing unit 232.

  The TFC control unit 231 controls the entire TFC in the HDD 1. Specifically, the output value (OUTPUT VALUE) to the heater 124 is set in the register of the AE 13 in accordance with the detected temperature (TEMPERATURE) detected by the temperature detector 19 such as a thermistor. The AE 13 has a drive circuit that drives the heater 124, and supplies an output (HEATER CURRENT) of a set output value to the heater 124. Typically, the AE 13 drives the heater 124 with constant current drive or constant voltage drive. That is, the AE 13 supplies a constant current or a constant voltage set by the TFC control unit 231 to the heater 124. In addition, the AE 13 may drive the heater 124 so that the output becomes constant power. The output to the heater 124 is changed not only by temperature but also by read / write processing.

  The TFC control unit 231 measures the resistance value of the heater 124 at a preset timing. Specifically, the AE 13 has a measurement circuit that measures the resistance value of the heater 124. The TFC control unit 231 instructs the AE 13 to be set to the test mode (MODE SET) at a predetermined timing and to measure the resistance value of the heater 124. The TFC control unit 231 requests the AE 13 to measure the resistance value by setting setting data in the control register of the AE 13. The AE 13 measures the resistance value of the heater 124 in response to a request from the TFC control unit 231.

  As a preferable example of the timing for measuring the resistance value of the heater 124, the TFC control unit 231 measures the resistance value at the time of power-on-reset (POR) when the HDD 1 is powered on. Alternatively, the TFC control unit 231 can measure the usage time of the HDD 1 and can start measuring the resistance value of the heater 124 when the measured time reaches a preset time. In addition, the TFC control unit 231 may perform resistance value measurement with reference to the use time in the specific temperature region.

  The TFC control unit 231 can measure the heater resistance values of the head slider 12 simultaneously or at different timings. For example, the TFC control unit 231 measures the usage time of each head slider 12 and measures the heater resistance value of only the head slider 12 when each usage time reaches a preset set time.

  Referring to the flowchart of FIG. 4, when the AE 13 measures the resistance value of the heater 124, the AE 13 stores the measured value in its own register (S11). The TFC control unit 231 accesses the register of the AE 13 and acquires a measured value (RESISTANCE VALUE) of the heater resistance. The TFC control unit 231 determines whether the acquired resistance measurement value is within a predetermined reference range (S12). When the resistance measurement value is within the reference range (YES in S12), the process ends. When the resistance measurement value is out of the reference range (NO in S12), the TFC control unit 231 executes an error handling process for the resistance failure (S13).

  As one of the error handling processes, the TFC control unit 231 notifies the host 51 that an abnormality (resistance failure) has been detected in the resistance value of the TFC heater 124 (ALERT). For example, the TFC control unit 231 stores resistance failure detection and data indicating the state in a register in the HDC / MPU 23. The host 51 can know that an abnormality of the heater resistance has occurred by referring to the register at a predetermined timing.

  As a preferable criterion for determining a resistance failure, the TFC control unit 231 is more preferable from the viewpoint of preventing an error due to a resistance failure in a range where the resistance value of the heater 124 has changed by 10% or more from its initial resistance value. The TFC control unit 231 determines that the resistance is defective in a range where the measured value changes by 5% or more from the initial resistance value. The measured value or the initial value may be corrected or changed according to the temperature detected by the temperature detector 19.

  FIG. 5 is a graph showing actual measured values of the heater resistance. An acceleration test was performed on a plurality of head sliders, and a change in resistance value of the heater 124 was measured. Specifically, as shown in FIG. 5, the power supplied to the heater 124 was gradually increased, and the heater resistance value with respect to the supplied power was measured. The measurement was performed on a plurality of head sliders.

  As understood from the graph of FIG. 5, when each initial value is set to 100%, the resistance value gradually decreases to 95%, and then rapidly changes from 95% to 85%. When the resistance value decreases to 85%, there is a failure mode in which the resistance value becomes infinite due to disconnection. Therefore, it is preferable that the TFC control unit 231 determines that the resistance is defective and warns the host 51 in a region where the resistance is reduced to 90% or less of the initial resistance value. In order to further improve the reliability, it is preferable that at least the TFC control unit 231 determines that the resistance is defective in the region of 95% or less where the resistance value starts abrupt change.

  Note that it may be determined that the resistance is defective when the area is at least 90% or 95% or less. For example, 97% may be used as a reference value, and the area below that may be determined as resistance failure. However, in order to avoid frequent warnings, it is important that the reference value is not too large. Accordingly, the TFC control unit 231 compares the measured resistance value with the reference value using 90% or 95% as a reference value, and can determine that the resistance is defective when the measured resistance value is equal to or less than the reference value.

  A preferred example of the error handling process is an increase in the measurement frequency of the resistance value of the heater 124. The TFC control unit 231 shortens the measurement time interval of the resistance value or starts measurement at a timing that has not been measured so far. For example, when the TFC control unit 231 performs the measurement every time the specified usage time elapses before the failure determination, the measurement is also performed in the POR after the failure determination, or the specified usage time for the measurement is shortened. As a result, it is possible to reduce the possibility of missing a sudden change in the resistance value thereafter.

  Another preferred example of the error handling process is slew rate control of the output to the heater 124. In order to reduce the deterioration of the heater 124, it is preferable to lower the slew rate of the output to the heater 124. The slew rate corresponds to the speed at which the output from the AE 13 to the heater 124 rises or falls. The rise or fall of the current and voltage to the heater 124 is fast at a high slew rate. On the other hand, at the low slew rate, the rise and fall of the current and voltage to the heater 124 is slow.

  Specifically, the slew rate can be expressed by the time from when the output from the AE 13 to the heater 124 starts changing until the saturation value is reached. For example, at the rising edge of constant current driving, the slew rate at the rising edge can be defined by the time from when AE13 starts to flow current until it reaches its saturation value. Similarly, at the falling edge of constant current driving, the slew rate at the falling edge can be defined by the time from when the output current of the AE 13 starts to decrease until the saturation value, that is, the time until it reaches the 0 level. In the case of constant voltage driving, it can be defined by the voltage value.

  As shown in FIG. 3, when it is determined that the resistance is defective, the TFC control unit 231 sets a lower slew rate value (SLEW RATE) in the setting register of the AE 13. The AE 13 outputs current / voltage to the heater 124 at a slew rate according to the setting. Degradation of the heater 124 can be suppressed by lowering the slew rate.

  Alternatively, it is preferable to perform a write and verify process in an error handling process under a predetermined condition. In the write and verify process, after the user data is written on the recording surface of the magnetic disk 11, it is confirmed whether the user data is correctly written. The HDC / MPU 23 performs the write and verify process in addition to or without performing notification (warning) to the host 51.

  When the resistance value of the heater 124 changes, the protrusion amount of the head element unit 122 changes depending on the driving method of the heater 124. Specifically, in the case of constant current driving, a decrease in resistance value results in a decrease in heater power and the amount of protrusion decreases. On the other hand, in the case of constant voltage drive, an increase in resistance value results in a decrease in heater power, and the amount of protrusion decreases. Therefore, the HDC / MPU 23 preferably performs the write and verify process under these error conditions in each driving method.

  Specifically, with reference to FIG. 3, when the TFC control unit 231 determines that the resistance is defective, the TFC control unit 231 notifies the read / write processing unit (RW processing unit) 232 of the determination result. The RW processing unit 232 controls and executes user data read / write processing. In the write operation, the RW processing unit 232 temporarily stores the user data (DATA) acquired from the host 51 in the buffer 241 in the RAM 24, and then extracts the user data from the buffer 241 and transfers it to the RW channel 21. . The data transferred to the RW channel 21 is transferred to the head slider 12 via the AE 13, and the head slider 12 writes the data to the target address (sector). In reading, the RW processing unit 232 stores the user data acquired from the RW channel 21 in the buffer 241. Thereafter, the RW processing unit 232 extracts user data from the buffer 241 and transfers it to the host 51.

  The RW processing unit 232 that has received the notification of the resistance failure performs a write and verify process under a predetermined condition. Preferably, the write and verify process is performed when the temperature detected by the temperature detector 19 is equal to or lower than a preset reference temperature. This is because insufficient data writing, particularly poor overwrite in the initial stage of writing, tends to occur in a low temperature region, while write and verify processing can lead to a decrease in the performance of the HDD 1.

  In the write and verify process, the RW processing unit 232 writes user data to the magnetic disk 11 and then reads the written data by the head element unit 12. The RW processing unit 232 compares the read data acquired from the RW channel 21 with the data stored in the buffer 241, and confirms that user data is correctly written on the magnetic disk 11. If the data has not been written correctly, the RW processing unit 232 re-executes the write process. The data actually read from the magnetic disk 11 can be all or a part of the written data. Since there are many errors at the initial stage of writing, it may be determined by comparing only a part of data at the initial stage of writing. The write and verify process may be performed regardless of the environmental temperature.

  Contrary to the resistance change described above, in constant current driving, an increase in resistance value results in an increase in heater power, and the amount of protrusion increases. On the other hand, in the constant voltage drive, the decrease in the resistance value increases the heater power, and the protrusion amount increases. Accordingly, it is preferable to reduce the current value or voltage value supplied to the heater 124 under these resistance error conditions in each driving method. If the resistance value is infinite (more than the reference value), the heater 124 does not function because it is in an open state. Accordingly, even in this case, it is preferable to perform the write and verify process as described above.

  In the above example, the TFC control unit 231 refers to only the resistance measurement value to determine whether or not to perform the error handling process, but it is one of preferable modes to refer to other conditions as well. In one preferred embodiment, the TFC control unit 231 refers to the error rate of the read user data.

  As shown in the block diagram of FIG. 6, the ECC processing unit 233 in the RW processing unit 232 performs ECC processing on user data. In the write process, the ECC processing unit 233 adds an ECC (Error Checking Code) to the data from the host 51. The data to which the ECC is added is transferred to the RW channel 21. In the read processing, the ECC processing unit 233 performs error correction processing using the ECC of the data transferred from the RW channel 21 and stores the error-corrected data in the buffer 241.

  In the error correction processing in reading, the ECC processing unit 233 counts the error rate, that is, the number of correction bits (number of error bits) per codeword. The TFC control unit 231 acquires data representing the error rate from the ECC processing unit, and determines whether or not to execute the error handling process according to the data. Specifically, the TFC control unit 231 specifies a change in the error rate with respect to the initial value of the error rate, and determines whether or not to execute the error handling process according to the change. The initial value can be registered in the HDD 1 in the manufacturing stage before shipment, for example.

  A preferred embodiment will be described with reference to the flowchart of FIG. The TFC control unit 231 uses two reference ranges for the measured resistance value. For example, the TFC control unit 231 sets a change in resistance value of less than 5% as the first reference range. Also, a resistance value change of less than 2% is used as the second reference range. The second reference range is a narrower range within the first reference range. Referring to FIG. 6, when AE 13 measures the heater resistance value (S21), TFC control unit 231 determines whether the measured resistance value is within the first reference range, that is, changes by 5% or more from the initial value. It is determined whether or not (S22). When the resistance value has changed by 5% or more (NO in S22), the TFC control unit 231 determines to execute the error handling process, and the HDC / MPU 23 executes it (S25).

  When the measured resistance value is within the first reference range, that is, when the change in resistance value is less than 5% (YES in S22), the TFC control unit 231 determines that the measured resistance value is within the second reference range (2% Or less) (S23). If the change in resistance value is in the second reference range, that is, if the measured change in resistance value is less than 2%, the process ends without performing the error handling process (S25). This is because this change is considered to be a measurement error or a normal range of the heater 124.

  When the change in resistance value is not within the second reference range, that is, when the measured change in resistance value is 2% or more and less than 5%, the TFC control unit 231 refers to the error rate. The TFC control unit 231 identifies a change in the error rate from the initial value, and determines whether the error rate exceeds a preset reference (S24). When the change in the error rate is within the reference range (YES in S24), the process ends without performing the error handling process (S25). When the error rate indicates a deterioration beyond the reference (NO in S24), the HDC / MPU 23 executes an error handling process (S25).

  As described above, by referring to the error rate in addition to the resistance value, the resistance failure of the heater 124 can be determined more reliably and accurately. In particular, by using a plurality of reference ranges for the resistance value and referring to the error rate in a gradual reference range, the heater 124 can be prevented from being opened / shorted. Note that the TFC control unit 231 may refer to the error rate indirectly by data representing the error rate or the data instead of directly representing the error rate or the change thereof. Further, the error rate or the reference range may be corrected depending on the temperature condition. This is the same for the read amplitude of the lower user data.

  In another preferred embodiment, the TFC control unit 231 refers to the read amplitude of the read user data in addition to the resistance measurement value. The TFC control unit 231 knows the read amplitude by acquiring the amplitude value from the register of the AE 13 or by acquiring the gain value (VGA in FIG. 6) of the VGA (Variable Gain Amplifier) from the RW channel 21. it can. The TFC control unit 231 identifies whether the change in the measured resistance value of the heater 124 and the change in the readout amplitude are in the same direction. When these changes are in the same direction, the TFC control unit 231 determines to execute the error handling process.

  For example, in constant current driving, an increase in heater resistance means a decrease in clearance. Therefore, the read amplitude is expected to increase. On the other hand, a decrease in heater resistance means an increase in clearance. Therefore, the read amplitude is expected to decrease.

  In constant voltage driving, an increase in heater resistance means an increase in clearance. Therefore, the read amplitude is expected to decrease. On the other hand, a decrease in heater resistance means a decrease in clearance. Therefore, the read amplitude is expected to increase. For example, the TFC control unit 231 can compare the initial value of the read amplitude registered in the manufacturing stage with the measured value and specify the direction and amount of change.

  In each heater driving method, the TFC control unit 231 determines that a resistance failure has occurred when the heater resistance and the change in readout amplitude are in the same direction. Preferably, the TFC control unit 231 has a plurality of reference ranges related to resistance values as in the determination with reference to the error rate, and also refers to the read amplitude in the determination of the resistance values in some of the ranges. To do. A specific processing method will be described with reference to the flowchart of FIG.

  In FIG. 8, the process from step S31 to step S33 is the same as the process from step S21 to step S23 in FIG. When the change in the resistance value is outside the second reference range (NO in S23), the TFC control unit 231 refers to the read amplitude and determines whether it is within the reference range (S34). For example, the TFC control unit 231 acquires the VGA gain value by the RW channel 21 and compares the initial value, and determines whether the change in the value is within the reference range. As described above, the reference range varies depending on the driving method of the heater 124. Further, the range varies depending on the direction of change of the resistance value, that is, whether the resistance value is increasing or decreasing. When the change in the read amplitude is within the reference range (YES in S34), the process ends without performing the error handling process, and when the change in the read amplitude is outside the reference range (NO in S34), the HDC / The MPU 23 executes error handling processing (S35).

  Specifically, when the heater resistance increases in constant current driving, if the read amplitude increases beyond the reference, the TFC control unit 231 determines that the resistance is defective. On the other hand, when the heater resistance is decreased, if the read amplitude is decreased more than the reference, the TFC control unit 231 determines that the resistance is defective. In the constant voltage drive, when the heater resistance increases, if the read amplitude decreases more than the reference, the TFC control unit 231 determines that the resistance is defective. On the other hand, when the heater resistance is decreased, if the read amplitude is decreased more than the reference, the TFC control unit 231 determines that the resistance is defective if the read amplitude is increased more than the reference.

  As mentioned above, although this invention was demonstrated taking preferable embodiment as an example, this invention is not limited to said embodiment. A person skilled in the art can easily change, add, and convert each element of the above-described embodiment within the scope of the present invention. For example, each of the above TFC examples can be applied to an HDD in which a head slider including only a read element or a write element is mounted, or to a disk drive device other than the HDD.

In this embodiment, it is a block diagram which shows typically the whole structure of HDD. In this embodiment, it is sectional drawing which shows typically the structure of the head slider provided with the heater for TFC. In this embodiment, it is a block diagram which shows typically the functional component relevant to the error handling corresponding to the case where the resistance value measurement of a TFC heater and a resistance value show an error. In this embodiment, it is a flowchart which shows the case which performs resistance defect determination with reference to the resistance measured value of a TFC heater. In this embodiment, it is a graph which shows the actual measured value of heater resistance with respect to heater power. In this embodiment, it is a block diagram which shows typically the functional component relevant to the resistance defect determination which referred the error rate or the read amplitude. In this embodiment, it is a flowchart which shows the case where resistance defect determination is performed with reference to the error rate of the user data read in addition to the resistance measurement value. In this embodiment, it is a flowchart which shows the case where resistance failure determination is performed with reference to the read amplitude of the read user data in addition to the resistance measurement value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hard disk drive, 10 Enclosure, 11 Magnetic disk 12 Head slider, 14 Spindle motor, 15 Voice coil motor s16 Actuator, 19 Temperature detector, 20 Circuit board 21 Read / write channel, 22 Motor driver Unit 23 Hard disk controller / MPU, 24 RAM, 31 Write element 32 Read element, 32a Magnetoresistive element, 33a, b Shield, 34 Protective film 51 Host, 121 Trailing side end face, 122 Head element part, 123 Slider 124 Heater, 231 TFC control unit, 232 read / write processing unit 241 buffer, 311 write coil, 312 magnetic pole, 313 insulating film

Claims (14)

A slider that floats on a rotating disk;
A head element portion disposed on the slider;
A heater that is disposed on the slider and adjusts a clearance between the disk by projecting the head element portion by thermal expansion;
A measurement circuit for measuring the resistance value of the heater at a preset timing;
A controller that determines whether the heater has a resistance failure with reference to the measured resistance value, and performs error handling processing when the resistance is defective,
A disk drive device comprising: The controller notifies the host of a resistance failure of the heater in the error handling process.
The disk drive device according to claim 1. The controller performs confirmation processing of user data written by the head element unit in the error handling processing.
The disk drive device according to claim 1. A temperature detector,
The controller performs confirmation processing of user data written by the head element unit when the temperature detected by the temperature detector is equal to or lower than a reference temperature.
The disk drive device according to claim 3. The heater is driven at a constant current,
The controller, when the resistance value of the heater has fallen outside the reference range, performs a confirmation process of user data written by the head element unit,
The disk drive device according to claim 3. The heater is driven at a constant voltage,
When the resistance value of the heater increases outside the reference range, the controller performs confirmation processing of user data written by the head element unit.
The disk drive device according to claim 3. The controller increases the frequency of measuring the resistance value of the heater in the error handling process.
The disk drive device according to claim 1. The controller reduces the slew rate of the output to the heater in the error handling process.
The disk drive device according to claim 1. The controller determines the heater as a defective resistance in a range where a change in the resistance value of the heater with respect to a preset value is 10% or more.
The disk drive device according to claim 1. The controller further refers to a read amplitude of the head element unit to determine a resistance failure of the heater;
The disk drive device according to claim 1. The controller further determines a resistance failure of the heater with reference to an error rate of data read from the head element unit,
The disk drive device according to claim 1. The controller performs the error handling process when the resistance value of the heater is outside the reference range and when the resistance value of the heater is within the reference range and the change in the read amplitude is outside the reference range.
The disk drive device according to claim 10. The controller performs the error handling process when the resistance value of the heater is outside the reference range and when the resistance value of the heater is within the reference range and the change in the error rate exceeds the reference.
The disk drive device according to claim 11. A slider that floats on a rotating disk, a head element portion disposed on the slider, and a heater that is disposed on the slider and projects the head element portion by thermal expansion to adjust a clearance between the disk, and A control method in a disk drive device comprising:
Measure the resistance value of the heater at a preset timing,
Refer to the measured resistance value to determine whether the heater has a resistance failure,
A method of performing error handling processing when it is determined that the resistance is defective.

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